<< Chapter < Page Chapter >> Page >

1. computer memory system and characteristics

1.1 computer memory overview

The memory is that part of computer where programs and data are stored. The basical concept is the following:

  • Bits

The basic unit of memory is the binary digit called a bit. A bit may contain a 0 or 1. It is the simplest possible unit

  • Memory addresses

- Memories consist of a number of cells or locations each of which can store a piece of information. Each location has a number called its address, by which program can refer to it. The cells is the smallest addressable

- If an address has m bits, the maximum number of cells addressable is 2m.

- Byte: 8-bits

- Bytes are grouped into words. The significance of word is that most instruction operate on entire word. A computer with a 32bit/word has 4 bytes/word

  • Byte ordering

- The bytes in a word can be numbered from left-to-right or right-to-left.

- The former system, where the numbering begin at the “big” (i.e, high-order) end is called a big endian computer, such as the SPARC or the big IBM mainframes. In contras it is a little endian computer, such as the Intel family using right-to-left numbering for the representation of a 32 bit computer.

1.2 characteristics of memory system

  • Capacity: the amount of information that can be contained in a memory unit -- usually in terms of words or bytes
  • Memory word: the natural unit of organization in the memory, typically the number of bits used to represent a number
  • Addressable unit: the fundamental data element size that can be addressed in the memory -- typically either the word size or individual bytes
  • Unit of transfer: The number of data elements transferred at a time – usually bits in main memory and blocks in secondary memory
  • Transfer rate: Rate at which data is transferred to/from the memory device
  • Access time:

– For RAM, the time to address the unit and perform the transfer

– For non-random access memory, the time to position the R/W head over the desired location

  • Memory cycle time: Access time plus any other time required before a second access can be started
  • Access technique: how are memory contents accessed

– Random access:

» Each location has a unique physical address

» Locations can be accessed in any order and all access times are the same

» What we term “RAM” is more aptly called

read/write memory since this access technique also applies to ROMs as well

» Example: main memory

– Sequential access:

» Data does not have a unique address

» Must read all data items in sequence until the desired item is found

» Access times are highly variable

» Example: tape drive units

– Direct access:

» Data items have unique addresses

» Access is done using a combination of moving to a general memory “area” followed by a sequential access to reach the

desired data item

» Example: disk drives

– Associative access:

» A variation of random access memory

» Data items are accessed based on their contents rather than their actual location

» Search all data items in parallel for a match to a given search pattern

» All memory locations searched in parallel without regard to the size of the memory

Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Computer architecture. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10761/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Computer architecture' conversation and receive update notifications?

Ask